Nest (National Employment Service and Training)
Nest (National Employment Service and Training) is a leadingtraining institute for ASNT level II. We are the only training centregiving 100% placement assistance to the candidates till candidatesget placed. Our trainers are having more than ten years of fieldexperience in industries like petroleum refineries and power plant(nuclear, thermal). The candidates will get both theoretical andpractical during the training session. We are moulding ourcandidates with advance training medium like visual and audio toenrich their knowledge. Our candidates will get a globallyauthentication certificates from ASNT America Society for NonDestructive Testing level II as per SNT-TC-1A standard onsuccessful completion of training and practical exams.Our candidates will get onsite training in the particular industrieslike refineries and power plant to get a real time experience. Nesttakes whole responsibilities of our candidates developing in theircareer. Other than NDT training, we are providing Motivation class,personality development session to get through in their interviewswith fear.
Vision: Nest Institute of NDT posse’s high quality international standard training for NDT in accordance with quality management system and pursuing placement for candidates to improve their career.Our Mission: To give quality training and education along with placement for the youngsters to enrich their career (or) to make their life delightful.
The earliest and most useful method of NDT isvisual examination. Important details can be collectedduring VT which would be useful for future analysisand also to decide on the types of NDT to be used foras further analysis. Also, VT should be carried out asa complementary method to all other NDT methods.VT should proceed and succeed all otherexaminations. Inaccessible areas can be inspected bymeans of boroscope and fiber-optic techniques.Depending upon the severity of the surface defectand the component in use, decision will be taken forsalvaging the component or not. If the product isfound unacceptable during visual examination itself,further NDT need not be carried out, thus savingtime and cost of inspection
Surface deposits Scaling Corrosion Discoloration Oxidation bulging Missing parts Mechanical damage Dimensional conformance Gross effects visible on the surface Distortion of components during fabrication and in services General corrosion on the surface of a component
Liquid penetrant testing (LPT) is another means of enhancing thecapability of visual examination. It is suitable for use on smoothsurfaces of all materials, magnetic as well as non-magnetic. It islimited to surface defects. Its inability to indicate the depth orbreadth of flaw should be kept in mind while selecting thismethod for particular application.Use of LPT for porous materials is ruled out since the absorptioninto the pores would mask the presence of defects. A clean surfaceis a pre-resist as penetrant cannot enter in to the cracks that arefilled with dirt, oil, or other matter.Size, shape, weight and number of workpieces to be inspectedoften influence the selection of a penetrant system. The desireddegree of sensitivity and the cost are the most important factors inselecting a system.LPT can also be used for leak testing. In this case, the componentcasting is filled with penetrant and developer is applied outsidethe surface.
LPT is selected for detecting the following types of discontinuities on the surface of a component. Cracks of any orientation Porosity Pin holes Voids Forging laps Forging bursts Lamination in plates Various types of weld defects Corrosion cracks Creep fissures Fatigue cracks
While LPT is effective only for fine surface discontinuities, the needremains to detect larger surface flaws or those present just below thesurface. The need is met by magnetic particle testing (MPT). Thistechnique is applicable only for ferromagnetic materials. MPT is aconsidered more sensitive than LPT. MPT requires a higher degree oroperator expertise to ensure that the magnetic fields are aligned in thecorrect direction in order to detect the defect. Flaws orientedperpendicular to the induced magnetic field is only reliably detectable.Hence the challenge is to induce magnetic field lines in a given work pieceso that they are most likely to be perpendicular to the flaw orientation.Therefore, prior knowledge on flaw orientation and or introduction ofmagnetic fields in several directions are is essential.It is commonly agreed that defects breaking the surface are most severeamongst the various discontinuities occurring in components. Fordynamically loaded structures, their removal is essential. Their detectionin ferrite materials is most easily accomplished by MPT. Since the depthdetermination of the surface breaking cracks is almost impossible, crackdepth measurements may be additionally employed to asses them.Detection of subsurface defects by MPT is impossible if the componentsare thin, but generally it requires ideal testing conditions.
MPT is used for detecting following discontinuities in ferromagnetic materials. Surface discontinuities: Cracks and tears Porosity Shrinking cavities Slag inclusions Voids Forging laps Grinding cracks Corrosion cracks Fatigue cracks Discontinuities just below the surface (within around 6mm depth from the surface sensitivity goes down as a defect is deeper): Larger size cracks in various orientations Pores Slag inclusions
The other NDT methods are used for detection of defectswhich are open to the surface nearer to the surface. Todetect more deeply seated discontinuities, NDT methodswith test medium capable of deeper penetration andsystem that senses even minute changes in thecharacteristics, behaviour of the test medium is required.Radiographic inspection is one of the most widely usedmethods of NDT as this is applied to all metals andalloys, both ferrous and nonferrous, for detection ofvolumetric type of defects. The range of capabilitiesoffered by the variety of sources and equipments hasbrought radiography to the forefront of NDT techniques.Testing of multilayer vessels and welds is generally adifficult task due to in accessible inner layers. RT is theonly NDT method to evaluate multilayered vesselsduring manufacturing stages and inservice.
Development of micro focal X-ray units has made it possibleto extend radiographic practice to meet the requirements ofmore stringent quality levels demanded for criticalapplications, besides a host of new applications. It is knowthat the sensitivity in radiography depends to a large extendon the focal spot size. In micro focal radiography, the focalspot size is less than 100microns and typically 15-50 micronas compared to a few mm or ½ a mm in conventionalradiography. Using microfocal RT, intricate geometricalcomponents such as tube to tube sheet. Welds can be testedwith a sensitivity of even 1% of wall thickness 0-3mm.microfocal RT can be used for detection of micro cracks ofaround 25micron in size. Another application of microfocalRT is to check the integrity of micro-welds used electronicintegrated circuits.One of the advantages of RT is that no prior preparation ofthe surface of the component is necessary. The maindisadvantage of the RT is the possible hazards due toexposure to radiation if proper care is not taken.
RT is selected to detect and size the following types of discontinuities Cracks (parallel to the radiation beam) Volumetric defects such as slag inclusions, voids etc: Porosity Blockages or deposits inside the pipe lines are pressure vessels Material thickness To detect hidden foreign material inside a component
Ultrasonic testing involves use of high frequency sound wavescoupled to the components to be inspected and studying thereflection pattern of these waves. UT is finding increasedapplications in various industries. Several wave modes such aslongitudinal, shear and surface waves can be used dependingon the orientation and location of the discontinuities. Differenttechniques such as pulse-echo, through transmission, andpitch-catch or employed. The advantages of UT are real timeavailability of results, higher penetrating power of thesewaves, higher sensitivity for planner defects, independencesensitivity over depths, low cost for inspection, higherportability to the equipment and compatibility for automation.But the subjectivity of the results on the operators training andskill is stumbling block for its wider acceptance. With theadvent of microprocessors and automation, operatordependability is being eliminated to a larger extent and UTfinding increased applications in industries such as power,railways, chemical, aerospace etc:
UT of cast metals and alloys is renderd difficult due tothe influence of casting intricacy, micro structuralvariations and surface roughness. Defects occurring inthe cast structure have irregular surfaces which scatterthe aquostic waves and makes UT more difficult. Hencesuccessful use of UT for inspection of castings dependsgreatly upon the skill and expertise of the operator.UT is the most suitable method of NDT for inserviceinspection (ISI) of components in power plants, chemicalprocess industries, etc:. Many times, RT cannot beapplied for ISI due to the requirements of two sideaccessibility. UT is more sensitive flaw growthmonitoring has compared with RT in view of all theseadvantages; the first choice of ISI is UT for volumetricdefects in components except for heat exchangers andcondensers where ECT is preferred.
UT Is Selected To Detect The Size The Following Type Of Discontinuities Surface breaking and hidden cracks in any orientation Inter granular cracks Laps Laminations Volumetric defects such slag inclusions, voids, ect Porosity Wall thickness measurements Creep Hydrogen encriptment Liquid level measurement To detect blockages, deposits, etc. in the pipe lines and pressure vessels
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